Short to ground
Thread Starter
Member
Joined: Apr 2010
Posts: 96
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From: NE Florida
2004 E55
Short to ground
Is it typical for these cars to show a short to ground at the trunk battery...because of the auxiliary battery or some other German engineering?
Test light between positive battery post and positive battery cable (disconnected from battery) lights up. I disconnected all the auxiliary power wires from the post, this was just the large positive cable itself. I tried the same at the auxiliary battery and test light did not light.
Normal or do I have an issue?
Test light between positive battery post and positive battery cable (disconnected from battery) lights up. I disconnected all the auxiliary power wires from the post, this was just the large positive cable itself. I tried the same at the auxiliary battery and test light did not light.
Normal or do I have an issue?
MBWorld Fanatic!
Joined: Jul 2012
Posts: 1,556
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From: Canada
07 E63 + 07 CLK63CAB
You just complete the circuit when you did this and any current flow will light up your tester, ie the trunk light or an open door will give you the same draw. Now as for the aux battery there may be no current flow so the light will no light up but also maybe that battery is toast, what is the issue why you are checking like this. Does the aux show voltage across neg and pos post?
Thread Starter
Member
Joined: Apr 2010
Posts: 96
Likes: 0
From: NE Florida
2004 E55
Yes. The aux battery is showing voltage across terminals.
Stopped for gas, car wouldn't restart. Ground cable from trunk battery was hot to touch at the battery terminal end. Took it off, let it cool, hooked it back up and car started normally.
Got home and found resistance across the ground cable to be high, but also checked for short to ground to see if there is something going on besides the ground cable.
Stopped for gas, car wouldn't restart. Ground cable from trunk battery was hot to touch at the battery terminal end. Took it off, let it cool, hooked it back up and car started normally.
Got home and found resistance across the ground cable to be high, but also checked for short to ground to see if there is something going on besides the ground cable.
MBWorld Fanatic!
Joined: Jul 2012
Posts: 1,556
Likes: 15
From: Canada
07 E63 + 07 CLK63CAB
Using a battery terminal cleaner wire brush, clean both the terminal on the battery as well as the terminal end on the cable to ensure good contact, also tighten up cable on the battery and then try to twist the cable on the terminal, sometimes although tight on the bolt the terminal is not.
Good catch though, check the body ground point also. Remove and buff with wire wheel, reinstall.
Sometimes refurbished batteries have the terminal shaved to appear new and they are smaller in diameter than a new battery terminal, hence the check by twisting after tightening.
Good catch though, check the body ground point also. Remove and buff with wire wheel, reinstall.
Sometimes refurbished batteries have the terminal shaved to appear new and they are smaller in diameter than a new battery terminal, hence the check by twisting after tightening.
